Rubber tire shredder

ABSTRACT

A tire shredder having a stripper plate to prevent feed from wrapping about a shaft on which feeder discs are mounted.

RELATED U.S. APPLICATION DATA

This application is a continuation-in-part of my application Ser. No.07/496,286 filed Mar. 20, 1990 now U.S. Pat. No. 5074479, which wassubject to an election requirement.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to shredding discarded rubber vehicletires.

2. Description of the Prior Art

Millions of pneumatic vehicle tire casings are discarded daily in theUnited States. Disposal and recycling efforts have problems. Buriedtires are an unstable fill because the tires tend to resurface as aresult of air pockets and the density of the rubber. Air pollutionproblems are created if casings are burned, especially if the casingsare not shredded to promote faster combustion.

There are tire shredding machines, but these have generally beenuneconomic. The shredders suffer from low output, high waterrequirements, frequent jamming, rapid dulling of cutter blades andbreakdowns.

Shredders have been built with a vertical passage leading to a pair oftransversely disposed cutter wheels on adjacent parallel shafts rotatingat different speeds. The cutter wheels have flat side walls thatpartially overlap, so that rotation results in a scissors actionreducing the rubber tires into manageable and disposable or burnableshreds.

Water has frequently used as a lubricant with the shredders by freelyspraying water into the cutting chamber. The casings are wetted byfreely spraying water into the cutting chamber. Heretofore the amountsof water have required an immediate source and a means of disposing ofsomewhat polluted water. The area around the shredders easily becomeswamplike.

STATEMENT OF THE OBJECTS

Accordingly, it is an objective of the present invention to increaseoutput, reduce jamming, increase cutting blade life and reducebreakdowns to produce a practical tire shredder.

Other objectives, advantages and novel features of the invention willbecome apparent to those skilled in the art upon examination of theinvention and the accompanying drawings.

SUMMARY OF THE INVENTION Brief Description of the Drawings

Further objectives and advantages of the invention will be apparent fromthe following detailed description, taken in conjunction with theaccompanying drawings illustrating a preferred embodiment of theinvention. The drawings are:

FIG. 1 is a prospective view of a stick type figure of the overallconfiguration of a shredder in accordance with the invention.

FIG. 2 is an opposite prospective view of a portion of FIG. 1 to show aportion of the initial conveyor.

FIG. 3 is an end view of the cutting chamber in accordance with theinvention.

FIG. 4 is a side view of the upper section of the cutting chamber inaccordance with the invention.

FIG. 5 is a top view of a cutter blade assembly in accordance with theinvention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

FIG. 1 schematically shows a shredder apparatus 20 for shredding rubbertires in accordance with this invention. Tire casings T are placed on afirst conveyor 21 to be delivered to the hopper 22 which sits atop acutting chamber 23.

The first conveyor 21 as shown in more detail in FIG. 2 has a roller 24adjacent the hopper 22 at the high end of the first conveyer 21. Theconveyer 21 is from 60 cm to 80 cm in width and the roller 24 as betterseen in FIG. 2 is modified to have a wheel 25 mounted outward of eachedge of first conveyer 21 on the roller 24. Each wheel 25 has a width ofabout 30 cm. The diameter of the wheels 25 is such that the surface ofthe wheel 25 is a side extension of the conveyor surface. The wheels 25rotate with the roller 24 so the surface of the wheels 25 is moving atthe same speed as the first conveyor 21. The surface of the wheels 25 isstudded with small nail like projections of about 1.5 cm for bettertraction when in contact with the casings T. The wheels 25 reduce thenumber of casings T falling from the first conveyor 21 and missing thehopper 22 and also reduces the variation of angles with which casings Tare fed into the hopper 22.

The first conveyor 21 includes a belt or diameter belt 26 to which angleirons 27 are attached at regular intervals of about 60 cms andperpendicular to the path of the conveyor to form projections 27. Theprojections 27 have a width of about 40 cms and project about 4 cms fromthe belt surface of the first conveyor 21. The projections 26 preventcasings T from sliding down the first conveyor 21. The casings T can behooked on a projection 27 or the outside of the casing T rested againsta projection 27. As modified, the first conveyor 21 can use a muchsteeper angle of incline than earlier conveyors provided for the samepurpose. The use of a steeper angle allows the shredder to operate inmore confined spaces.

The entrance 30 of the hopper 22 is disposed off the ground a sufficientdistance so that gravity assists the casings T to fall into hopper 22which sits atop the cutting chamber 23 and assists the shredded scraps Sto fall from an exit 31 of the cutting chamber 23. From the exit 31 thescraps S fall to a second conveyor 32 for removal to a bin 33 or othercollection means for hauling to a suitable disposal or use site.

The shredding is accomplished in the cutting chamber 23. In theshredding process the tire casings are reduced to small shreds S. Theshreds S vary in size, the major dimension being typically less than 5cms. Smaller shreds and more uniform sizing can be achieved by recyclinga portion of the output back to the cutting chamber 23 or positioning asecond cutting chamber to receive the output of the first chamber 23.Recycling reduces processing capacity and multiple chambers adds cost.

Preferably, the apparatus 20 is sized to be mountable on a truck trailerto provide mobility. The apparatus 20 is moved to accumulations ofcasings rather than casings moved to the apparatus 20. An immobileshedder is uneconomical.

Looking downward the cutting chamber 23 is about a 1.5 meters wide andabout 1.0 meter in length. FIG. 3 is a side view of the hopper 22 andchamber 23. At the entrance to the chamber 23 in the lower portion ofthe hopper is a pair of parallel feed shafts 34 and 35. In the chamber23 adjacent and below the paired feed shafts 34 and 35 is a pair ofparallel cutter shafts 36 and 37.

Mounted on each feed shaft 34 and 35 at intervals are star shaped discs38; the points or fingers 39, preferably 6, of the discs 38 are bluntedat the tips 40 and spaced to engage the casings loosely and pull thecasings T downward when the shaft 34 on the left is rotated clockwiseand the shaft 35 on the right is rotated counter clockwise. Gravity andthe downward motion imparted to the casings T move the casings into thepath of the cutter shafts 36 and 37.

The rotational speed of the feed shafts 34 and 35 are equal. Therotational speed of feed shafts 34 and 35 are also set relative to therotational speed of the cutter shafts 36 and 37. Preferably, theseshafts are all driven with a single engine or power means 41 and drivenwith gearing means to adjust the various speeds of rotation. There is anrpm difference between one cutter shaft and the other cutter shaft offrom 12 to 20 rpm. The feed shafts 34 and 35 rotate at the same speedand at the same rpm as the slower of the cutter shafts. Preferably theengine for the shredder apparatus has a transmission so that the rpm ofthe slower cutter shaft can be slowed to increase torque. Preferably 6to 8 rpm is used for truck tires and 45 to 60 rpm is used for passengercars.

The hopper 22 has spray nozzles 43 mounted at spaced intervals about itsperiphery just above the level of the feed shafts 34 and 35. The nozzles43 are positioned to deliver a mist to the interior of the hopper 22.Six nozzles 43 spaced evenly along each side should be sufficient. Inoperation, approximately 65 gallons per hour are used. Passing the waterthrough a 10 micron screen prior to feeding the water to the nozzlesreduces clogging of the nozzles and allows smaller nozzle openings andhence less water to be needed. The apparatus 20 is equipped with a 1000gallon water tank 44 which should be sufficient for a day's operation.

The discs 38 mounted on the feeder shafts 34 and 35 have an outsidediameter of about 20 cm. The interval between discs 38 is about 15 cm,center to center. Typically the star shaped discs 38 have six fingers 39to the star and each finger extends 7.5 cm inward from the tip 40. Thetip 40 is blunted. The width of the star is 1.25 cm and the center 38 ishollow and shaped for mounting on the shafts 34 or 35. As shown thecenter is cylindrical could be hexagonal or other shape. The discs 38are fixedly mounted to the shafts 34 and 35 to rotate with them.

The shafts 34 and 35 are mounted spaced apart to have the tips 40 on theopposing shafts no closer than 10 cm widthwise. The discs 38 on eachshaft are mounted not opposite a disc 38 on the other shaft but spacedevenly between two adjacent discs 38 on the other shaft so that thediscs 38 alternate from shaft to shaft and intermesh with wide spacing.

Past shredders have had feed type shafts but they have jammedfrequently. The fingers 39 tend to bring casings not only downward buton around up against the outside walls of the cutting chamber 23 to jam.Mounted to the walls of the cutting chamber 23 to prevent jamming arestripper plates 45 between each pair of discs 38. Each plate 45 extendsthe width between adjacent discs 38 about 13 cm. Clearance between thesides of the plate 45 and disc 38 is not critical and is about 1 cm. Theplate 45 extends inward from the chamber wall and below the adjacentfeed shaft and inward of the feed shaft to have a surface 46 parallel tothe level of the center lines of the shafts 34 and 35. The surface isabout 2.5 cm by 13 cm. Clearance between plates 45 and the adjacent feedshaft is not critical and is about 1 cm.

Mounted on each cutter shaft 36 and 37 as shown in FIG. 5 at preciseintervals are a series of cutter bundles 50 comprising two slitterblades 51 and 52 sandwiching a grabber disk 53. The interaction ofcutter bundles 50 combine to shear and slice the casings to achieve theshredding.

The bundles 50 as mounted are interspaced with the bundles 50 on theother shaft so they alternate and interlock. The precise interval iscrucial being 0.005 to 0.010 cm wider than the width of the opposinginterspaced bundle 50. The interval is maintained by mounting firstspacer disks 54 on the cutter shafts between the bundles 50. The widthof the cutter bundles 50 is also crucial and must be maintained within a0.0012 cm tolerance. In addition the radius of the first spacer 54 isimportant as it controls the size of the shreds moving downward past theshafts and out of the apparatus 20. The outside radius of the firstspacer 54 and outside radius of the bundle 50 and space between adjacentbundles on the same shaft is the area through which the shreds mustpass.

In use as described in more detail later, the slitter blades 51 and 52are sharpened by milling the side which reduces the thickness of theslitter blade. The blades 51 and 52 are designed for four to sixsharpenings either on one side or some on each side. After eachsharpening, to maintain the critical bundle 50 thickness a second spacer55 is added between one slitter blade and its adjacent grabber disk 53.The thickness of the second spacer 55 replaces the thickness removed bythe milling of the slitter blades of the bundle 50. A thicker secondspacer 55 is needed after each sharpening.

The slitter blades 51 and 52 are made of high quality steel. The outsideradius is about 7 cm plus or minus 0.05 mm. The initial thickness is 2cm plus or minus 0.05 mm. The blades are circular as seen in FIGS. 6 and7 with cutouts 60 at 2 cm intervals of 0.5 cm depth and 2 cm length.

A shearing action is achieved by the series of rotating cutter bundles50 mounted on the shafts alternating to interlock so that their sidefaces 56 lie close together and act like scissors as the shafts 36 and37 are rotated. The following side of the cutout 60 and outside surfaceof the adjacent slitter blade act like continuously rotating scissorblades.

Wear occurs primarily on the following side of the cutout 60 on theslitter blades 51 and 52 occurs adjacent the distal side face of blade.Dullness reduces the efficiency and a number of actions are available torenew the effectiveness of the blade. One is to switch the place ofslitter blades of a bundle 50 relative to the grabber disk 53. This usesthe same following side for the scissor action but adjacent the oppositeside face of the blade.

Similarly the slitter blade can be reversed in place or interchangedwith a slitter blade on the opposite shaft. This switches the leadingside for the following side of the cutout 60. These proceduressignificantly increase slitter blade life.

The slitter blades are resharpened by milling off the side face of theslitter blade approximately 3 mm. The loss in thickness of the slitteris accounted for by adding a second spacer 55 or adjusting the thicknessthereof.

The grabber 53 is a circular disk having projecting teeth. A secondmaterial 61 is mounted on the teeth to absorb the wear. A purpose of theteeth is to assist the movement of the carcasses down between the cuttershafts 36 and 37.

I claim:
 1. A tire casing shredder including in combination:a. a chamberhaving a vertical passage therethrough, b. a pair of horizontallymounted parallel feed shafts supported rotatably at the entrance to thechamber in the passage way, c. a series of feeder discs, being generallystar-shaped to have multiple fingers and blunt tips, mounted on eachfeed shaft so that the discs alternate from shaft to shaft and intermeshwith wide spacing, d. a stripper plate mounted to the wall of thecutting chamber to extend inward to and along one of the feed shafts inthe space between two adjacent feeder discs and below the feed shaft andthen upward and inward of the feed shaft to have a surface parallel tothe level of the center line of the feed shaft.